Conventionally, as solid electrolytic capacitors, a resin mold sealed type solid electrolytic capacitor in which a capacitor element is sealed by molding a synthetic resin or a box sealed type solid electrolytic capacitor in which a capacitor element is sealed by a box-shaped case are well known.
For example, as shown in Patent Document 1 listed below, in the box sealed type solid electrolytic capacitor, in a state in which a capacitor element is accommodated inside a case main body having a bottom wall and peripheral side walls provided at peripheral four sides (outer peripheral edge portions) of the bottom wall, an upper opening of the case main body is closed in a sealed manner by an upper lid.
In such a solid electrolytic capacitor, an anode lead of the capacitor element is electrically connected to an anode circuit pattern by welding processing. In cases where the anode lead and the anode circuit pattern are spatially distanced, there exists a case in which the anode lead is electrically connected to the anode circuit pattern via a conductive auxiliary member made of, e.g., a metal member (hereinafter referred to as “bolster member”). The anode lead and the bolster member are generally connected them by welding processing.
In general, the anode lead of the solid electrolytic capacitor is structured by valve action metal, and the surface of the anode lead is covered by a natural oxide film. Therefore, when connecting a bolster member to the anode lead, it is difficult to electrically connect using conductive material such as a silver paste.
For this reason, conventionally, the oxide film of the anode lead at the contact portion of the anode lead and the bolster member is broken by resistance welding, so that the anode lead is electrically and mechanically connected to the bolster member by welding.
Concretely, when performing resistance welding, one of welding electrodes is connected to the anode circuit pattern and the other welding electrode is connected to the upper side of the anode lead of the capacitor element, and electric current is applied in series while pressuring them to perform welding so that the anode lead and the bolster member are connected electrically and mechanically.